Electrodynamic vs. Piezoelectric – Why Low Frequencies Matter for Underwater Sound
Choosing the right transducer technology for lakes and professional pools.
When it comes to underwater sound reproduction, not all transducers are created equal. For years, the industry relied on piezoelectric technology, but for those needing to reproduce frequencies below 1000Hz, the limitations are significant. In this article, we explore why the electrodynamic principle used by Akuasound is the superior choice for portable and safe underwater audio.
The Limitations of Piezoelectric Sources
Traditional piezoelectric transducers (Fig. 2) are often inefficient at low frequencies. Due to their frequency-dependent electrical impedance, they require extremely high supply voltages—often in the range of 1000V—to compensate for low transmission sensitivity. This poses a massive safety risk and operational challenge, especially when working on small boats or in pool environments with non-specialized personnel.
The Electrodynamic Advantage
The Akuasound source operates on an electrodynamic principle, similar to a high-quality loudspeaker. It features a permanent magnet, a moving coil, and an emission membrane.
Key benefits include:
Linear Frequency Response: Unlike piezo sources that peak around 10 kHz, the electrodynamic source offers a flat response across the entire audio band (20 Hz to 20 kHz).
Enhanced Low-End: It is specifically designed to excel at frequencies below 1000Hz, where piezo sources typically fail.
Safety First: It operates at low DC voltages (maximum 36V), drastically simplifying safety protocols and making it ideal for compact, portable systems.
Operational Simplicity: The system does not require static pressure
compensation as depth varies, reducing costs and the risk of accidental damage.
fig. 3 – Response in the source stream
Laboratory Validation
Tests in laboratory tanks have confirmed a robust emission extension toward low frequencies. While some irregularities appear above 5 kHz due to potential nodal lines on the membrane, the performance in the target low-frequency range remains consistent and reliable, moving according to its fundamental vibration mode without interference.
